Amanda/Monster has a few attacks.
When she raises a fist and strikes the ground nothing can block that, you have to jump or dodge before she hits the ground (that attack appears under you and explodes).
But she throws a simular attack at you that the rocks will stop, which is the attack she does most of the time.
And some times if close she'll throw the wave/cone attack, you have to be moving and dodge as she is starting it to get out of the way of that one, if you wait until you see it it's too late doh.
So yes, some of her attacks won't hit you if you are behind a large rock (any of them will stop her attacks that are air borne).